1. Technical Field
The present invention relates to a compact rotary joint for the connection of single or multimode fibers that is capable of maintaining low connection losses when exposed to severe shock, vibration and temperature environments.
2. Background Art
In fiber optic waveguide transmission, rotary joints are required when there is a necessity to transmit optical signals between two turnable or rotatable members. Fiber optic rotary joints have been used infrequently, however, because of their high cost and design limitations.
For example, one approach to fiber optic rotary joint design has been to expand the beam and collimate it prior to passing through a rotary joint. The beam is then refocused and aligned with the receiving fiber optic. This method is used to reduce axial misalignment and to reduce sensitivity to contamination, but has several significant limitations.
This form of rotary joint is large and expensive due to the complexity required to maintain lens alignments with the fiber optics across the joint. Further, the axial alignment is critical to reduce insertion losses and is limited by bearing designs. This design feature restricts the use of such joints to benign environments, with limited operational ranges of temperature, vibration, shock and rates of angular rotation.
As a result of these factors, the performance of prior art rotary joints is marginal, with typical insertion losses for single mode fibers greater that 1 dB and return loss of 20 dB using high quality lenses.